Safety screw



E. RIPAMONTI ET-AL SAFETY SCREW Filed July 23. 1920 22/2) ezzfb'o g man'lt Z Peal-@12 'Pmma Aug. 26, 1924.

PATENT OFFICE.

ETTOBE RIPAMONTI AND ENIBIIC O PEIRANO', F MILAN, ITALY.

SAFETY SCREW.

Application filed July 23, 1920. Serial no. 398,600.

To all whom it may conce'm:

Be it known that we, Er'ronn RIPAMONTI and Emnco PEIRANO, subjects of the King of Italy, and residents of Milan, Italy, have invented certain new and useful Improvements in Safety Screws, of which the following is a specification.

The present invention relates to a safety- Fig. 1 shows an elevation view of a screw with milled 'head; 2 is a plan view-of the same.

L' e numbers of reference indicate similar parts on the two figures.

The screw is formed by the, threaded shank 1- and the milled head 2-. According to the present invention, the

head of the screw is provided with a fiat surface 2 extendin diametrically across the same and having its central portion enlar ed to form a circular area 2". Semi-annu ar segments 5 and 6 are arranged on oppositei sides of said flat surface and form part of the head. These semi-annular segments have their centers coaxial .with the axis of the screw, andeach of said segments has a substantially vertical end wall 3, 4 extending tures.

radially from the axis of the screw. The upper face of each segment is inclined gradually downwardly from its own end wall to the flat surface 2 With this construction,-a screw driver or the like 7 placed 40 against the walls 3 and 4 may be used to turn the screw in a clockwise direction, but if an attempt is made to unscrew the screw by means of the tool 7, the screw driver will ride upwardly on the segments 5 and 6.

It is understood that. the invention also may be applied to the turned leading screws.

Having now particularly described and ascertained the nature of our invention and in what manner the same is performed, we declare that what we claim is:

A screw having a head circular in crosssection and provided with a flat upper surface extending diametrically entirely across the head and having its intermediate portion enlarged to form a circular area, a plurality of semi-annular se ments arranged on opposite sides of said at surface, forming part of the head and having their centers coaxial with the axis of the screw, each of said segments having a substantially vertical end wall extending radially from the axis of the screw, the upper face of each segment being inclined graduallydownwardly from its own end wall to said flatsurface.

In witness whereofwe aflix our signa- ETTORE RIPAMONTI. ENRICO PEIRANO.

the upper surfaces of 45' 

